Trying to run code at end of 'Yatzy Scoring'...

from copy_1 import D6

class Hand(list):
    '''Provide number(8) and type(die_class) of dice to roll
    ...then use these to append dice to our list
    die_class = Add arg to hold class that all Dice will be'''
    def __init__(self, size=8, die_class=None, *args, **kwargs):

        '''If no die_class provided...'''
        if not die_class:
            raise ValueError("\n\n*****\nPlease provide a die_class\n*****")
        super().__init__()

        ''' Pluggable requirement to load list with a num of 
        die_class objects'''
        for _ in range(size):
            self.append(die_class())

        '''Call sorting method'''
        self.sort()

        '''Add utility that returns all dice with a certain value
            Best used in subclasses in 'larger than one hand' app'''
        def _by_value(self, value):
            dice = []
            for die in self:
                if die == value:
                    dice.append(die)
            return dice


class YatzyHand(Hand):
    def __init__(self, *args, **kwargs):
        super().__init__(size=5, die_class=D6, *args, **kwargs)

    ''' Properties for each hand of one value '''
    @property
    def ones(self):

        return self._by_value(1)
    @property
    def twos(self):
        return self._by_value(2)
    @property
    def threes(self):
        return self._by_value(3)
    @property
    def fours(self):
        return self._by_value(4)
    @property
    def fives(self):
        return self._by_value(5)
    @property
    def sixes(self):
        return self._by_value(6)

    ''' Return map where keys = die value, value = how many of 
    that value are in each hand'''
    @property
    def _sets(self):
        return {
            1: len(self.ones),
            2: len(self.twos),
            3: len(self.threes),
            4: len(self.fours),
            5: len(self.fives),
            6: len(self.sixes)}


class YatzyScoresheet:
    ''' Ones '''
    def score_ones(self, hand):
        return sum(hand.ones)
    ''' Twos '''
    ''' Threes'''
    ''' etc.'''

    ''' Method to score dice by num items in a set '''
    def _score_set(self, hand, set_size):
        scores = [0]
        for worth, count in hand._sets.items():
            if count == set_size:
                scores.append(worth*set_size)
        return max(scores)

    ''' Method scores a single pair, i.e., 2 items from hand'''
    def score_one_pair(self, hand):
        return self._score_set(hand, 2)


hand = YatzyHand()
three = D6(value=3)
four = D6(value=4)
one = D6(value=1)
hand[:] = [one, three, three, four, four]
print(YatzyScoresheet().score_one_pair(hand))